<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let str = 'abcd efg hijk';
        var falg_1 = str.startsWith("abcd");
        console.log(falg_1);
        var falg_2 = str.endsWith("jk");
        console.log(falg_2);
        //----------------
        console.log('xy'.repeat(100));
    </script>
</body>

</html>